1. Field of the Invention
This invention relates to a cement composition. More particularly, it relates to a cement composition excelling in a slump retaining property capable of preventing the so-called cement compounds such as, for example, cement paste, mortar, and concrete from the degradation of flowability by aging.
2. Description of the Prior Art
Since the early deterioration of concrete structures aroused a serious social issue in 1981, the necessity for enhancing the workability and durability of concrete by decreasing the unit water volume in concrete has been eagerly demanded. Among the ensuant endeavors toward satisfying this demand are counted such technical innovations as concern the cement dispersant, an agent capable of producing a huge effect on the quality and performance of the cement compounds.
Heretofore, the fluidifying method which comprises producing freshly mixed concrete having the fluidity (hereinafter described as "slump") thereof lowered by the incorporation of an AE agent or AE water-decreasing agent at a plant, transporting the freshly mixed concrete on a mobile concrete mixer to the site of concrete placement, and fluidifying the concrete in the mixer by the addition of a fluidifying agent and heightening the slump to a prescribed level has been in vogue. This method, however, has many problems such as, for example, the public nuisance caused by the noise and the waste gas which arise when the fluidifying agent added to the concrete is mixed by stirring in the mobile concrete mixer, the ascription of the responsibility for the quality of the produced fluidified concrete, and the conspicuous decline of the slump of the fluidified concrete by aging.
In the circumstances, various admixture producers have made energetic studies devoted to the development of a so-called high quality AE water decreasing agent which fits direct addition to the freshly mixed concrete at the concrete plant. At present, naphthalene type, aminosulfonic acid type, and polycarboxylic acid type high quality AE water decreasing agents are marketed. In all these high quality AE water decreasing agents available in the market, the polycarboxylic acid type high quality AE water decreasing agents have the outstanding feature of possessing the highest water decreasing ratio. They nevertheless are on a par with the other high quality AE water decreasing agents in occasionally failing to attain thorough preclusion of slump loss under such harsh use conditions as are encountered when the produced freshly mixed concrete is transported in the summer to a remote site of placement.
An object of this invention, therefore, is to provide a cement composition excelling in the slump retaining property.